1-Arylnaphthalene Lignan: A Novel Scaffold for Type 5

J. Med. Chem. 1999, 42, 1293-1305

1293

1-Arylnaphthalene Lignan: A Novel Scaffold for Type 5 Phosphodiesterase Inhibitor Tatsuzo Ukita,* Yoshinori Nakamura, Akira Kubo, Yasuo Yamamoto, Masami Takahashi, Jun Kotera,† and Tomohiro Ikeo† Discovery Research Laboratory, Tanabe Seiyaku Company, Ltd., 3-16-89, Kashima, Yodogawa, Osaka 532-8505, Japan, and 2-2-50, Kawagishi, Toda, Saitama 335-8505, Japan Received December 14, 1998

1-Arylnaphthalene lignan, which had been reported as a PDE4 inhibitor by Iwasaki, was disclosed as a new structural class of PDE5 inhibitors. The structural requirements for potent and specific PDE5 inhibition were revealed in a 1-arylnaphthalene lignan series, in which 1-(3bromo-4,5-dimethoxyphenyl)-5-chloro-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-2-(methoxycarbonyl)naphthalene hydrochloride (27q) showed the most potent and specific inhibition (PDE5 inhibition IC50 ) 6.2 nM, selectivity for PDE5 against PDE1, -2, -3, and -4 >16 000). It is noteworthy that 27q has the best selectivities against PDE isoforms among PDE5 inhibitors so far reported. Compound 27q exhibited almost the same relaxant effects on rat aortic rings as sodium 1-[6-chloro-4-[(3,4-methylenedioxybenzyl)amino]quinazolin-2-yl]piperidine-4-carboxylate (35) (27q, EC50 ) 0.10 µM; 35, EC50 ) 0.20 µM) and was selected for further biological evaluation. Introduction Cyclic nucleotide phosphodiesterases (PDEs) are key enzymes for catalyzing the hydrolysis of cyclic nucleotides, cAMP and cGMP, to their respective 5′-nucleoside monophosphates. PDEs have been classified into at least seven distinct isoenzyme families,1 which have been distinguished by their substrate specificities, the mechanisms of regulation, and their sensitivity to various pharmacological agents. PDE5, cGMP-specific PDE, is distributed in lung, kidney, spleen, endothelial cells, smooth muscle cells, etc., and plays a key role for biological regulations by means of hydrolysis of cGMP in these tissues. Because cGMP mediates vasorelaxant actions, the potent and selective PDE5 inhibitor is an attractive target for treatment of hypertension, angina, congestive heart failure, and impotence.2 Potent and selective PDE5 inhibitors have been extensively reported, but a majority of them are classified into three categories: zaprinast-related inhibitors,3 quinazoline derivatives,4 and phthalazine derivatives.5 Iwasaki et al. in our company reported a series of 1-aryl-2,3-bis(hydroxymethyl)naphthalene lignans as selective PDE4 inhibitors.6 In connection with our efforts in search of biologically active lignans, we now disclose 1-arylnaphthalene lignans having potent and specific PDE5 inhibitory activities. It is noteworthy that both selective PDE4 and PDE5 inhibitors are derived from the common scaffold, 1-arylnaphthalene lignan, and the spectra of PDE inhibitions are entirely altered by the chemical modification of its substituents. Chemistry The key intermediates 9, 1-aryl-2,3-bis(methoxycarbonyl)naphthalene lignans, were synthesized by the Diels-Alder reaction of isobenzofurans 7 with dimethyl †

Tanabe Seiyaku Co., Ltd., Saitama.

fumarate, followed by acid-mediated ring opening of 1,4epoxides 8 and subsequent dehydration7 (Scheme 1). As shown in Scheme 1, the precursors of isobenzofuran (3 and 6) were prepared by the following two methods: bromoacetals 1 were transformed into cyclic acetals 3 via hydroxy acetals 28 (method A), and lactols 6 were obtained from phthalides 5 which were converted from amides 49 (method B). The Diels-Alder adducts 8 were afforded by the reaction of 3 or 6 with dimethyl fumarate as a dienophile in the presence of acetic acid in a one-pot procedure. Aromatization of 8 proceeded well by treatment with trifluoroacetic acid or BF3‚Et2O via ring opening of 1,4-epoxides and subsequent dehydration to provide the key intermediates 9 in good yields. 9a was found to be a seed compound from the random screening of 1-arylnaphthalene lignans6 on PDE5 inhibition. 9a was divided into three parts (A-C rings), and the modification of each part was carried out in the following procedures: (i) transformation of the methoxycarbonyl moiety on 2,3-positions of arylnaphthalene (B ring); (ii) conversion of 1-aryl group and/or substituents on 1-aryl group as the C ring; and (iii) replacement of substituents on the A ring. The transformation of substituent on 2,3-positions of 9a is outlined in Scheme 2. 3-Carboxylactone 11 was prepared by selective oxidation of the 3-hydroxymethyl group of diol 10 that was obtained from 9a by the reduction of ester groups with Red-Al. Alkaline hydrolysis of the ester group of 9a proceeded in a highly selective manner to provide 2-methoxycarbonyl-3-carboxy compound 12a because of the steric hindrance of the 1-(3,4,5-trimethoxyphenyl) ring. Corresponding 2-carboxylactone 13 was selectively prepared by the reduction of 12a with sodium borohydride via the activated mixed anhydride. 3-Amino-2-hydroxymethyl compound 14 was obtained by means of Curtius rearrangement of acyl azide derived from 12a, followed by reduction of 13 with LiAlH4.

10.1021/jm9807048 CCC: $18.00 © 1999 American Chemical Society Published on Web 03/23/1999

1294

Journal of Medicinal Chemistry, 1999, Vol. 42, No. 7

Ukita et al.

Scheme 1a

a Reagents: (a) n-BuLi, R2CHO/THF, or n-BuLi then ClTi(Oi-Pr) , R2CHO/THF; (b) dimethyl fumarate, AcOH/toluene; (c) s-BuLi, 3 TMEDA, R2CHO/THF; (d) DIBAL/CH2Cl2; (e) TFA or BF3‚OEt2. b 9a-p were prepared by method A. c 9q-s were prepared by method B.

Condensation of 12a with ammonia or secondary amines afforded amides 16, 18-24, and 27a in good yields, whereas that with methylamine resulted in providing a mixture of amide 17 and imide 28, which were isolated by silica gel column chromatography. Alcohols 25 and 26 were obtained from the reduction of ketone 24 and ester 22 with NaBH4 in good yields, respectively. Scheme 3 summarizes the synthesis of reduced analogues of 27a. Amine 31, the reduced analogue of the amide on the 3-position of 27a, was prepared from 2-methoxycarbonyl-3-methyl analogue 29, which was produced by the Diels-Alder reaction of isobenzofuran 7a with methyl crotonate. Bromination of 29 with N-bromosuccinimide was followed by substitution with 4-(2-hydroxyethyl)piperazine to provide amine 31 in a moderate yield. 2-Hydroxymethyl analogue 34, accompanied by the excessively reduced amine 33, was obtained from O-tert-butyldimethylsilyl compound 32 by treatment with LiAlH4. Biological Results and Discussion The compounds reported in this paper were first evaluated for inhibitory activities against the three different forms of PDEs isolated from canine cardiac ventricle (PDE1 and -3) and lung (PDE5) in vitro (Tables 1-3). Compounds selected on the basis of the PDE5 inhibitory activity were next evaluated for the relaxant effects

on rat aortic rings and additionally investigated for the two different forms of PDEs isolated from canine adrenal gland (PDE2) and lung (PDE4) (Table 4). From the random screening of 1-arylnaphthalene lignans on PDE inhibition, we found that 9a had a relatively selective PDE5 inhibitory activity (IC50 ) 2.1 µM, selectivity for PDE5 over PDE1 and -3 > 50). Transformation of the substituents on the 2,3-positions of 9a was first examined (Table 1). The importance of both or either ester group on the 2,3-positions of 9a is evident from the comparison of PDE5 inhibitory activities and isozyme selectivities between 9a and bis(hydroxymethyl) compound 10, the corresponding reduced product of 9a. Both 2-carboxy and 3-carboxy lactones 11 and 13, the imide 28, and amides 16-18, having carbonyl groups on 2- and/or 3-positions, were synthesized to investigate the structure-activity relationships (SAR) of 1-arylnaphthalene lignans. 3-Carboxylactone 11 was 30 times more potent than 9a (IC50 ) 0.068 µM), though it exhibited remarkably worse selectivities for PDE5 over PDE1 and -3 than 9a. 2-Carboxylactone 13, the corresponding regioisomer of 11, showed drastically changed PDE inhibition spectra and potent PDE1 and -3 inhibitory activities, with less PDE5 activity. The imide 28, 2-methoxycarbonyl-3amide 16, and 2-methoxycarbonyl-3-methylamide 17 markedly lost PDE5 inhibitory activities (IC50 > 100 µM), whereas 2-methoxycarbonyl-3-dimethylamide 18

1-Arylnaphthalene Lignan

Journal of Medicinal Chemistry, 1999, Vol. 42, No. 7 1295

Scheme 2a

a Reagents: (a) Red-Al/THF; (b) AgCO /benzene; (c) NaOH /MeOH; (d) (1) ClCOOEt, NEt /THF, (2) NaN , (3) heat/toluene, (4) concd 3 aq 3 3 HCl; (e) LiAlH4/THF; (f) (1) ClCOOEt, NEt3/THF, (2) NaBH4, (3) NaH/DMF; (g) amine, NH3, or CH3NH2, EDCl‚HCl-HOBt or CDI; (h) NaBH4/EtOH; (i) NaBH4/MeOH-THF.

showed an improved PDE5 inhibitory activity (IC50 ) 0.23 µM) with retained isozyme selectivities. Next we focused on the synthesis of 3-tertiary amides 19 and 20 based on the above results. Morpholino, 4-oxopiperidino, 4-hydroxypiperidino, and 4-(hydroxymethyl)piperidino amides 23-26, having oxygen atom in, on, or close to the 4-position of the six-membered ring, exhibited similar PDE5 inhibitory activities to dimethyl amide 18 and improved isozyme selectivities. Among the cyclic amides, 3-(2-hydroxyethyl)piperazino amide 27a showed a potent PDE5 inhibitory activity (IC50 ) 0.094 µM) and improved selectivities for PDE5 over PDE1 and -3 (selectivity ratios: 436 and 1063, respectively). 27a was selected as a lead compound, and the corresponding reduced products of 27a were synthesized in order to confirm the role of the carbonyl group on 2and/or 3-positions toward PDE5 inhibitory activity. 4-(2Hydroxyethyl)piperazinomethyl analogue 31, the reduction product of amide carbonyl, resulted in a considerable loss of activity (IC50 ) 2.4 µM). On the other hand,

2-hydroxymethyl analogue 34, the reduction product of methyl ester, exhibited marked loss of PDE1, -3, and -5 inhibitiory activities (IC50 > 100 µM for PDE1, -3, and -5). The 2-methoxycarbonyl and 3-[4-(2-hydroxyethyl)piperazino]carbonyl groups were fixed from the results of the above SAR study about the substituent on 2,3-positions of 27a. Next we looked at the replacement of the 1-aryl group, 1-(3,4,5-trimethoxyphenyl) group, with the phenyl group having a variety of substituents, the heteroaryl group, or the trans-styryl group (Table 2). Among mono-, di-, and trisubstituted phenyl compounds, 3-halogeno-4,5dimethoxyphenyl derivatives 27c and 27d only possessed increased potencies compared with 3,4,5-trimethoxyphenyl 27a (27c, IC50 ) 0.049 µM; 27d, IC50 ) 0.024 µM; 27a, IC50 ) 0.094 µM). Replacement by heteroaryl groups (27j and 27k) and the trans-styryl group (27l) led to remarkable loss of PDE5 inhibitory activities (IC50 >100 µM). Finally we investigated the effects of substituent on the A ring toward PDE5 inhibitory activity (Table 3).

1296


Ukita et al.

Scheme 3a

a Reagents: (a) (1) n-BuLi, 3,4,5-(OMe) PhCHO/THF, (2) methyl crotonate, AcOH/toluene, (3) TFA; (b) NBS, (PhCO) O /CCl ; (c) 1-(23 2 2 4 hydroxyethyl)piperazine/THF; (d) TBS-Cl, imidazole/THF; (e) LiAlH4/THF.

Scheme 4a

a

Reagents: (a) NaOHaq/MeOH; (b) 1-(2-hydroxyethyl)piperazine, DCC, HOBt/CH2Cl2.

Removal of substituents (27o) and introduction of an alkoxy, alkyl, and/or chloro substituent on 5,6,7-positions (27m,q-s) showed potent PDE5 inhibitory activities similar to 27d. Introduction of the methoxy group on the 8-position (27n) resulted in marked loss of not only PDE5 but also PDE1 inhibitory activity (IC50 > 100

µM). From the modification of the substituent on the A ring, 5-chloro analogue 27q showed the best inhibitory activity against PDE5 (IC50 ) 0.0062 µM), with markedly improved selectivities against PDE1 and -3 isoforms. We selected seven compounds on the basis of the



Table 1. Structures and PDE Inhibitions


a IC 50 values were determined from the logarithmic concentration-inhibition curve (at least four points). The value is given as the mean of three experiments, where the variation from the mean value is (20% or less. a IC 50 values were determined from the logarithmic concentration-inhibition curve (at least four points). The value is given as the mean of three experiments, where the variation from the mean value is (20% or less.

PDE5 inhibitory potency and isozyme selectivities for the evaluation of their relaxant effects on rat aortic rings and inhibitory activities of two additional and different forms of PDEs (PDE2 and -4), as shown in Table 4. Sodium 1-[6-chloro-4-[(3,4-methylenedioxybenzyl)amino]quinazolin-2-yl]piperidine-4-carboxylate (35) was selected as a reference compoud. These compounds were examined for relaxant effects on isolated rat aortic rings precontracted with phenylephrine (3 µM). The EC50 values of these compounds were well-

correlated with the inhibitory activities toward PDE5 as shown in Table 4.

It was ascertained that 27q exhibited a highly selective PDE5 inhibitory activity against not only PDE1 and -3 but also PDE2 and -4 (>16 000). It is noteworthy that

1298



a IC 50 values were determined from the logarithmic concentration-inhibition curve (at least four points). The value is given as the mean of three experiments, where the variation from the mean value is (20% or less.

Table 4. PDE Inhibitions and Relaxant Effects on Rat Aorta for Selected Compounds PDE inhibition, IC50, µMa II III IV

compd

I

27a 27c 27d 27m 27o 27p 27q 35

41 26 11 61 3.4 13 >100 4.7

>100 >100 >100 >100 >100 >100 >100 15

>100 >100 >100 >100 >100 >100 >100 >100

>100 >100 >100 >100 >100 >100 >100 3.4

V

relaxant effect EC50, µMb

0.094 0.049 0.024 0.017 0.025 0.012 0.0062 0.0016

2.0 1.3 0.46 0.30 0.79 0.56 0.10 0.20

a IC 50 values were determined from the logarithmic concentration-inhibition curve (at least four points). The value is given as the mean of three experiments, where the variation from the mean value is (20% or less. b EC50 values were determined from the logarithmic concentration-relaxation curve. The value is given as the average of two experiments, where the variation from the mean value is (30% or less.

27q showed the best selectivities against PDE isoforms (PDE1, -2, -3, and -4), among PDE5 inhibitors so far reported. Conclusion We discovered that 1-arylnaphthalene lignans have potent and specific PDE5 inhibitory activities and indicated that the spectra of PDE inhibitions are entirely altered by the chemical modification of substitutents on the common scaffold, 1-arylnaphthalene lignan. This finding will be beneficial for the design of specific PDE5 inhibitors in the other structural class. Among the analogues, 27q showed the most potent and specific PDE5 inhibitory activity (IC50 ) 6.2 nM, isozyme selectivities > 16 000) and exhibited potent effects on relaxation of rat aortic rings (EC50 ) 0.10 µM). 27q was selected for further evaluation as a treatment of cardiovascular diseases. Experimental Section General. Melting points were determined on a Bu¨chi 535 capillary melting point apparatus and are uncorrected. El-

Ukita et al. emental analyses were performed on a Perkin-Elmer 2400II analyzer. IR spectra were recorded on a Shimadzu IR-420 spectrophotometer. 1H NMR spectra were obtained on a Bruker AC-200 instrument (200 MHz) with TMS as an internal standard. Mass spectra were recorded on a Hitachi M-2000A spectrometer. Column chromatography was performed with silica gel (E. Merck, 70-230 mesh). Reactions were monitored by TLC using 0.25-mm silica gel F-254 (E. Merck) glass plates. n-Butyllithium was the 1.6 M solution in hexane and sec-butyllithium was the 1.3 M solution in cyclohexane supplied by Asia Lithium Co. General Procedure for the Preparation of Dimethyl Ester of 1-Arylnaphthalene Derivatives 9. Method A (Scheme 1). Compounds 9a,c-h,j-p were essentially prepared by the same procedure. The sequence is illustrated for 9a, followed by analytical data for 9c-h,j-p. 6,7-Dimethoxy-2,3-bis(methoxycarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (9a). To a solution of acetal 1 [R1 ) 4,5-(OMe)2] (58.2 g, 0.20 mol) in THF (300 mL) was added n-BuLi (131 mL, 0.21 mol) at -78 °C under a nitrogen atmosphere. After the mixture stirred at the same temperature for 30 min, a solution of the 3,4,5-trimethoxybenzaldehyde (39.2 g, 0.20 mol) in THF (100 mL) was added, and the reaction mixture was stirred at the same temperature for 30 min. The mixture was poured into H2O and extracted with AcOEt. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. A mixture of the residue, dimethyl fumarate (28.8 g, 0.20 mol), and acetic acid (100 mL) in toluene (100 mL) was heated under reflux for 2 h. After cooling to room temperature, TFA (5 mL) was added to the reaction mixture and the mixture was stirred at room temperature overnight. The mixture was poured into saturated aqueous NaHCO3 and extracted with CHCl3. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. Crystallization of the residue from Et2O gave 9a (49.8 g, 53%): mp 186-187 °C; 1H NMR (CDCl3) δ 3.68 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.95 (s, 6H), 4.03 (s, 3H), 6.61 (s, 2H), 6.95 (s, 1H), 7.25 (s, 1H), 8.46 (s, 1H); EIMS m/z 470 (M+, base), 455, 439, 344. 1-(3-Chloro-4,5-dimethoxyphenyl)-6,7-dimethoxy-2,3bis(methoxycarbonyl)naphthalene (9c): yield 43%; mp 165-168 °C; 1H NMR (CDCl3) δ 3.69 (s, 3H), 3.80 (s, 3H), 3.85 (s, 3H), 3.94 (s, 3H), 3.97 (s, 3H), 4.03 (s, 3H), 6.80-6.90 (m, 2H), 7.02 (d, 1H, J ) 1.9 Hz), 7.25 (s, 1H), 8.47 (s, 1H). 1-(3-Bromo-4,5-dimethoxyphenyl)-6,7-dimethoxy-2,3bis(methoxycarbonyl)naphthalene (9d): yield 37%; mp 178-179 °C; 1H NMR (CDCl3) δ 3.69 (s, 3H), 3.80 (s, 3H), 3.81 (s, 3H), 3.94 (s, 3H), 3.96 (s, 3H), 4.03 (s, 3H), 6.86 (s, 1H), 6.68 (d, 1H, J ) 1.9 Hz), 6.89 (d, 1H, J ) 1.9 Hz), 7.25 (s, 1H), 8.46 (s, 1H); EIMS m/z 518/520 (M+, base), 487/489. 6,7-Dimethoxy-2,3-bis(methoxycarbonyl)-1-(2-methyl4,5-dimethoxyphenyl)naphthalene (9e): yield 63%; mp 162-164 °C; 1H NMR (CDCl3) δ 1.93 (s, 3H), 3.61 (s, 3H), 3.75 (s, 3H), 3.81 (s, 3H), 3.94 (s, 3H), 3.95 (s, 3H), 4.03 (s, 3H), 6.65 (s, 1H), 6.73 (s, 1H), 6.81 (s, 1H), 7.27 (s, 1H), 8.47 (s, 1H); EIMS m/z 454 (M+, base), 422, 407. 6,7-Dimethoxy-2,3-bis(methoxycarbonyl)-1-(3,4-methylenedioxyphenyl)naphthalene (9f): yield 57%; mp 169170 °C; 1H NMR (CDCl3) δ 3.68 (s, 3H), 3.79 (s, 3H), 3.94 (s, 3H), 4.02 (s, 3H), 6.03 (d, 1H, J ) 1.4 Hz), 6.07 (d, 1H, J ) 1.4 Hz), 6.72-6.99 (m, 4H), 7.23 (s, 1H), 8.44 (s, 1H); EIMS m/z 424 (M+, base), 393. 1-(3,4-Dichlorophenyl)-6,7-dimethoxy-2,3-bis(methoxycarbonyl)naphthalene (9g): yield 75%; mp 185-187 °C; 1H NMR (CDCl ) δ 3.67 (s, 3H), 3.79 (s, 3H), 3.94 (s, 3H), 4.03 3 (s, 3H), 6.72 (s, 1H), 7.18-7.31 (m, 2H), 7.49 (d, 1H, J ) 2.0 Hz), 7.56 (d, 1H, J ) 8.2 Hz), 8.47 (s, 1H); EIMS m/z 448 (M+, base), 417. 1-(3,5-Dichlorophenyl)-6,7-dimethoxy-2,3-bis(methoxycarbonyl)naphthalene (9h): yield 65%; mp 153-155 °C; 1H NMR (CDCl ) δ 3.69 (s, 3H), 3.81 (s, 3H), 3.94 (s, 3H), 4.03 3 (s, 3H), 6.72 (s, 1H), 7.20-7.36 (m, 3H), 7.47 (t, 1H, J ) 1.9 Hz), 8.47 (s, 1H); EIMS m/z 448 (M+, base), 417. 1-(2-Bromo-4-pyridyl)-6,7-dimethoxy-2,3-bis(methoxy-



carbonyl)naphthalene (9j):10 yield 60%; mp 192-194 °C; 1H NMR (CDCl3) δ 3.68 (s, 3H), 3.80 (s, 3H), 3.95 (s, 3H), 4.04 (s, 3H), 6.65 (s, 1H), 7.3-7.37 (m, 2H), 7.55 (d, 1H, J ) 0.7 Hz), 8.48-8.58 (m, 2H); EIMS m/z 459/461 (M+, base), 428/430. 6,7-Dimethoxy-2,3-bis(methoxycarbonyl)-1-(3,4,5-trimethoxystyryl)naphthalene (9l): yield 57%; mp 166-168 °C; 1H NMR (CDCl3) δ 3.88 (s, 3H), 3.90 (s, 3H), 3.92 (s, 6H), 3.95 (s, 3H), 3.98 (s, 3H), 4.04 (s, 3H), 6.76 (s, 2H), 6.81 (d, 1H, J ) 16.5 Hz), 7.23 (s, 1H), 7.32 (d, 1H, J ) 18.1 Hz), 7.37 (s, 1H), 8.38 (s, 1H); EIMS m/z 496 (M+, base). 1-(3-Bromo-4,5-dimethoxyphenyl)-6-ethoxy-7-methoxy2,3-bis(methoxycarbonyl)naphthalene (9m): yield 42%; mp 171-173 °C; 1H NMR (CDCl3) δ 1.56 (t, 3H, J ) 7.0 Hz), 3.69 (s, 3H), 3.79 (s, 3H), 3.84 (s, 3H), 3.94 (s, 3H), 3.95 (s, 3H), 4.25 (q, 2H, J ) 7.0 Hz), 6.86 (S, 1H), 6.89 (d, 1H, J ) 1.9 Hz), 7.18 (d, 1H, J ) 1.9 Hz),7.23 (s, 1H), 8.44 (s, 1H); EIMS m/z 532/534 (M+, base). 1-(3-Bromo-4,5-dimethoxyphenyl)-6,7,8-trimethoxy2,3-bis(methoxycarbonyl)naphthalene (9n): yield 66%; mp 199-202 °C; 1H NMR (CDCl3) δ 3.36 (s, 3H), 3.61 (s, 3H), 3.83 (s, 3H), 3.91 (s, 3H), 3.92 (s, 3H), 3.93 (s, 3H), 4.01 (s, 3H), 6.83 (d, 1H, J ) 1.9 Hz), 7.05-7.15 (m, 2H), 8.46 (s, 1H); EIMS m/z 548/550 (M+, base), 470. 1-(3-Bromo-4,5-dimethoxyphenyl)-2,3-bis(methoxycarbonyl)naphthalene (9o): yield 56%; mp 153-156 °C; 1H NMR (CDCl3) δ 3.70 (s, 3H), 3.84 (s, 3H), 3.96 (s, 3H), 3.97 (s, 3H), 6.88 (d, 1H, J ) 1.9 Hz), 7.16 (d, 1H, J ) 1.9 Hz), 7.507.70 (m, 3H), 7.93-8.09 (m, 1H), 8.63 (s, 1H); EIMS m/z 458/ 460 (M+, base), 443/445, 427/429. 1-(3-Bromo-4,5-dimethoxyphenyl)-2,3-bis(methoxycarbonyl)-6-methoxynaphthalene (9p): yield 22%; mp 151153 °C; 1H NMR (CDCl3) δ 3.68 (s, 3H), 3.83 (s, 3H), 3.95 (s, 9H), 6.86 (d, 1H, J ) 1.9 Hz), 7.14 (d, 1H, J ) 1.9 Hz), 7.197.29 (m, 2H), 7.53 (d, 1H, J ) 9.1 Hz), 8.50 (s, 1H); EIMS m/z 488/490 (M+, base), 457/459. 1-(3-Amino-4,5-dimethoxyphenyl)-6,7-dimethoxy-2,3bis(methoxycarbonyl)naphthalene (9b):6 yield 81%; mp 196-198 °C; 1H NMR (CDCl3) δ 1.50-1.70 (br s, 2H), 3.68 (s, 3H), 3.80 (s, 6H), 3.91 (s, 3H), 3.93 (s, 3H), 4.02 (s, 3H), 6.33 (d, 1H, J ) 1.8 Hz), 6.39 (d, 1H, J ) 1.9 Hz), 6.70 (s, 1H), 7.22 (s, 1H), 8.42 (s, 1H). 6,7-Dimethoxy-2,3-bis(methoxycarbonyl)-1-(3-nitrophenyl)naphthalene (9i). To a solution of acetal 1 [R1 ) 4,5(OMe)2] (5.82 g, 20 mmol) in THF (40 mL) was added n-BuLi (12.5 mL, 20 mmol) at -78 °C under a nitrogen atmosphere. After stirring at the same temperature for 30 min, ClTi(Oi-Pr)3 (1 M in hexane, 20 mL, 20 mmol) was added and the mixture was stirred at the same temperature for 30 min. After 3-nitrobenzaldehyde (3.02 g, 0.20 mol) in 20 mL of THF was added, the reaction mixture was warmed to room temperature. After stirring for 30 min, the mixture was poured into diluted hydrochloric acid and extracted with AcOEt. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. A mixture of the residue, dimethyl fumarate (2.88 g, 20 mmol), and acetic acid (10 mL) in toluene (30 mL) was heated under reflux for 2 h. After evaporation of the solvent, the residue was dissolved in a mixture of CHCl3 (50 mL) and TFA (10 mL). After stirring at room temperature overnight, the reaction mixture was poured into saturated aqueous NaHCO3 and extracted with CHCl3. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. The residue was crystallized from Et2O to afford 9i (4.6 g, 54%): mp 194-196 °C; 1H NMR (CDCl3) δ 3.62 (s, 3H), 3.74 (s, 3H), 3.95 (s, 3H), 4.04 (s, 3H), 6.63 (s, 1H), 7.29 (s, 1H), 7.62-7.80 (m, 2H), 8.25-8.40 (m, 2H), 8.52 (s, 1H); EIMS m/z 425 (M+, base), 394. General Procedure for the Preparation of Dimethyl Ester of 1-Arylnaphthalene Derivatives 9. Method B (Scheme 1). Compounds 9q-s were essentially prepared by the same procedure. The sequence is illustrated for 9q, followed by analytical data for 9r,s. 3-(3-Bromo-4,5-dimethoxyphenyl)-7-chlorophthalide (5q). To a stirred mixture of 2-chloro-N-methylbenzamide (4a) (12.5 g, 73.8 mmol) and N,N,N′,N′-tetramethylethylenediamine

(TMEDA) (22.3 mL, 148 mmol) in THF (30 mL) was added s-BuLi (125 mL, 163 mmol) at -78 °C under a nitrogen atmosphere, and the mixture was stirred at the same temperature for 15 min. To this mixture was added dropwise 3,4,5trimethoxybenzaldehyde (18.1 g, 73.8 mol) in 300 mL of THF. After stirring at the same temperature for 30 min, the reaction mixture was poured into a mixture of H2O and AcOEt. The organic layer was separated, washed with brine, dried over MgSO4, and concentrated under reduced pressure. A solution of the residue in concentrated hydrochloric acid (10 mL)dioxane (100 mL) was heated under reflux for 2 h. After evaporation of the organic solvent, the residue was diluted with H2O and extracted with CHCl3. The organic layer was washed successively with saturated aqueous NaHCO3 and brine, dried over MgSO4, and concentrated under reduced pressure. The residue was crystallized from Et2O to give 5q (19.2 g, 68%): mp 165-168 °C; 1H NMR (CDCl3) δ 3.83 (s, 3H), 3.86 (s, 3H), 6.26 (s, 1H), 6.69 (d, 1H, J ) 1.9 Hz), 7.07 (d, 1H, J ) 1.9 Hz), 7,34-7.35 (m, 1H), 7,50-7.60 (m, 1H), 7.90 (d, 1H, J ) 8.2 Hz); EIMS m/z 384/382 (M+, base), 303. 1-(3-Bromo-4,5-dimethoxyphenyl)-5-chloro-2,3-bis(methoxycarbonyl)naphthalene (9q). To a stirred solution of 5q (5.0 g, 13 mmol) in CH2Cl2 (50 mL) was added diisobutylaluminum hydride (DIBAL) (1.5 M in toluene, 9.6 mL, 14.3 mmol) at -78 °C under a nitrogen atmosphere, and the mixture was stirred at the same temperature for 30 min. After addition of 1 mL of acetic acid, the reaction mixture was washed with brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure. A mixture of the residue, dimethyl fumarate (1.87 g, 13 mmol), and acetic acid (8 mL) in toluene (24 mL) was refluxed for 3 h. After evaporation of the solvent, the residue was diluted with AcOEt and washed successively with aqueous NaHCO3 and brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure to give 1-(3-bromo-4,5-dimethoxyphenyl)-5chloro-2,3-bis(methoxycarbonyl)-1,4-epoxy-1,2,3,4-tetrahydronaphthalene. The crude product was used in the next step without further purification. A mixture of the crude product and boron trifluoride etherate (BF3‚Et2O) (3.2 mL, 26 mmol) in CH3CN (50 mL) was heated at 50 °C for 5 h. The reaction mixture was poured into saturated aqueous NaHCO3 and extracted with AcOEt. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. Crystallization of the residue from i-Pr2O gave 9q (3.45 g, 54%): mp 133-135 °C; 1H NMR (CDCl3) δ 3.70 (s, 3H), 3.84 (s, 3H), 3.96 (s, 3H), 4.00 (s, 3H), 6.85 (d, 1H, J ) 1.9 Hz), 7.13 (d, 1H, J ) 1.9 Hz), 7.41-7.62 (m, 2H), 7.70 (dd, 1H, J ) 7.0, 1.6 Hz), 9.06 (d, 1H, J ) 0.7 Hz); EIMS m/z 492/ 494 (M+, base), 461/463. 1-(3-Bromo-4,5-dimethoxyphenyl)-7-chloro-2,3-bis(methoxycarbonyl)naphthalene (9r): yield 39%; mp 145148 °C; 1H NMR (CDCl3) δ 3.69 (s, 3H), 3.85 (s, 3H), 3.96 (s, 3H), 3.97 (s, 3H), 6.84 (d, 1H, J ) 1.9 Hz), 7.13 (d, 1H, J ) 1.9 Hz), 7.50-7.62 (m, 2H), 7.94 (m, 1H), 8.60 (s, 1H); EIMS m/z 492/494 (M+, base). 1-(3-Bromo-4,5-dimethoxyphenyl)-2,3-bis(methoxycarbonyl)-7-methylnaphthalene (9s): yield 83%; mp 120-122 °C; 1H NMR (CDCl3) δ 2.47 (s, 3H), 3.69 (s, 3H), 3.84 (s, 3H), 3.96 (s, 3H), 3.97 (s, 3H), 6.86 (d, 1H, J ) 1.8 Hz), 7.14 (d, 1H, J ) 1.8 Hz), 7.35 (s, 1H), 7.44 (dd, 1H, J ) 8.3, 1.4 Hz), 7.89 (d, 1H, J ) 8.3 Hz), 8.58 (s, 1H); EIMS m/z 472/474 (M+, base), 457/459, 441/443. 2,3-Bis(hydroxymethyl)-6,7-dimethoxy-1-(3,4,5-trimethoxyphenyl)naphthalene (10). To a stirred suspension of 3a (2.0 g, 4.25 mmol) in THF (20 mL) was added dropwise Red-Al (70% in toluene, 3.07 g, 10.6 mmol) at -10 °C, and the mixture was stirred at 0 °C for 1 h. After dropwise addition of MeOH (1 mL) and 20% aqueous NaOH (6 mL), the mixture was stirred at 50 °C for 30 min. The reaction mixture was poured into a mixture of H2O and AcOEt and extracted with AcOEt. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (CHCl3-MeOH ) 10:1) gave 10 (1.47 g, 83%): mp 124-126 °C; 1H NMR (CDCl3)

1300


Ukita et al.

δ 3.59-4.15 (br s, 2H), 3.75 (s, 3H), 3.84 (s, 6H), 3.96 (s, 3H), 4.01 (s, 3H), 4.65 (s, 2H), 4.93 (s, 2H), 6.59 (s, 2H), 6.79 (s, 1H), 7,14 (s, 1H), 7.73 (s, 1H); EIMS m/z 414 (M+, base), 396. 2-(Hydroxymethyl)-6,7-dimethoxy-1-(3,4,5-trimethoxyphenyl)naphthalene-3-carboxylic Acid Lactone (11). A mixture of 10 (1.5 g, 3.62 mmol) and AgCO3 (3.0 g, 10.9 mmol) in benzene (30 mL) was refluxed for 3 h. The solid was filtered off and washed with CHCl3. The filtrate was concentrated under reduced pressure, and the residue obtained was crystallized from AcOEt to give 11 (1.1 g, 74%): mp 240-242 °C; 1H NMR (CDCl3) δ 3.86 (s, 3H), 3.87 (s, 3H), 3.98 (s, 3H), 4.06 (s, 3H), 5.27 (s, 2H), 6.60 (s, 2H), 7.14 (s, 1H), 7.32 (s, 1H), 8.33 (s, 1H); EIMS m/z 410 (M+, base), 395, 379. General Procedure for the Preparation of 12. Compounds 12a-s were essentially prepared by the same procedure. The sequence is illustrated for 12a, followed by analytical data for 12b-s. 6,7-Dimethoxy-2-(methoxycarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene-3-carboxylic Acid (12a). A solution of 3a (30 g, 63.8 mmol) in a mixture of MeOH (200 mL) and 2 N aqueous NaOH (63.8 mL) was refluxed for 30 min. After evaporation of the organic solvent, the residue was acidified with 2 N hydrochloric acid and extracted with CHCl3. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. Crystallization of the residue from Et2O gave 12a (27.4 g, 94%): mp 222-224 °C; 1H NMR (DMSO-d6) δ 3.54 (s, 3H), 3.70 (s, 3H), 3.758 (s, 3H), 3.762 (s, 6H), 3.93 (s, 3H), 6.61 (s, 2H), 6.97 (s, 1H), 7.65 (s, 1H), 8,48 (s, 1H), 13,14 (br s, 1H); SIMS m/z 456 (M+),425 (base). 1-(3-Amino-4,5-dimethoxyphenyl)-6,7-dimethoxy-2(methoxycarbonyl)naphthalene-3-carboxylic acid (12b): yield 97%; 1H NMR (CDCl3) δ 3.68 (s, 3H), 3.81 (s, 3H), 3.81 (s, 3H), 3.92 (s, 3H), 4.03 (s, 3H), 5.66 (br s, 3H), 6.36 (d, 1H, J ) 1.8 Hz), 6.41 (d, 1H, J ) 1.9 Hz), 7.00 (s, 1H), 7.24 (s, 1H), 8.52 (s, 1H); EIMS m/z 441 (M+), 423, 409 (base). 1-(3-Chloro-4,5-dimethoxyphenyl)-6,7-dimethoxy-2(methoxycarbonyl)naphthalene-3-carboxylic acid (12c): yield 84%; mp 209-212 °C dec; 1H NMR (DMSO-d6) δ 3.53 (s, 3H), 3.70 (s, 3H), 3.82 (s, 3H), 3.85 (s, 3H), 3.93 (s, 3H), 6.85 (s, 1H), 6.92-7.01 (m, 2H), 7.67 (s, 1H), 8.50 (s, 1H), 13.0813.30 (br s, 1H); SIMS m/z 4460 (M+ + 1), 429 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-6,7-dimethoxy-2(methoxycarbonyl)naphthalene-3-carboxylic acid (12d): yield 98%; mp 228-230 °C; 1H NMR (DMSO-d6) δ 3.54 (s, 3H), 3.70 (s, 3H), 3.82 (s, 3H), 3.84 (s, 3H), 3.93 (s, 3H), 6.86 (s, 1H), 7.02 (d, 1H, J ) 1.9 Hz), 7.08 (d, 1H, J ) 1.9 Hz), 7.67 (s, 1H), 8.51 (s, 1H), 13.00-13.40 (br s, 1H). 6,7-Dimethoxy-2-(methoxycarbonyl)-1-(2-methyl-4,5dimethoxyphenyl)naphthalene-3-carboxylic acid (12e): yield 87%; mp 202-204 °C dec; 1H NMR (CDCl3) δ 1.94 (s, 3H), 3.62 (s, 3H), 3.76 (s, 3H), 3.82 (s, 3H), 3.96 (s, 3H), 4.04 (s, 3H), 6.66 (s, 1H), 6.74 (s, 1H), 6.82 (s, 1H), 7.29 (s, 1H), 8.57 (s, 1H); EIMS m/z 440 (M+), 408 (base). 6,7-Dimethoxy-2-(methoxycarbonyl)-1-(3,4-methylenedioxyphenyl)naphthalene-3-carboxylic acid (12f): yield 99%; mp 255-256 °C; 1H NMR (DMSO-d6) δ 3.51 (s, 3H), 3.67 (s, 3H), 3.93 (s, 3H), 6.13 (d, 2H, J ) 2.0 Hz), 6.73 (dd, 1H, J ) 7.9, 1.7 Hz), 6.81 (s, 1H), 6.84 (d, 1H, J ) 1.5 Hz), 7.04 (d, 1H, J ) 7.9 Hz), 7.64 (s, 1H), 8.48 (s, 1H), 13.17 (br s, 1H); EIMS m/z 410 (M+), 378 (base). 1-(3,4-Dichlorophenyl)-6,7-dimethoxy-2-(methoxycarbonyl)naphthalene-3-carboxylic acid (12g): yield 98%; mp 248-250 °C dec; 1H NMR (DMSO-d6) δ 3.51 (s, 3H), 3.68 (s, 3H), 3.93 (s, 3H), 6.70 (s, 1H), 7.32 (dd, 1H, J ) 8.3, 2.0 Hz), 7.57 (d, 1H, J ) 2.0 Hz), 7.69 (s, 1H), 7.78 (d, 1H, J ) 8.3 Hz), 8.53 (s, 1H); EIMS m/z 434 (M+), 402 (base). 1-(3,5-Dichlorophenyl)-6,7-dimethoxy-2-(methoxycarbonyl)naphthalene-3-carboxylic acid (12h): yield 95%; mp 239-241 °C; 1H NMR (DMSO-d6) δ 3.52 (s, 3H), 3.69 (s, 3H), 3.94 (s, 3H), 6.69 (s, 1H), 7.37 (d, 2H, J ) 1.9 Hz), 7.69 (s, 1H), 7.77 (t, 1H, J ) 1.9 Hz), 8.54 (s, 1H), 13.24 (br s, 1H); EIMS m/z 434 (M+), 402 (base).

6,7-Dimethoxy-2-(methoxycarbonyl)-1-(3-nitrophenyl)naphthalene-3-carboxylic acid (12i): yield 93%; mp 249-250 °C dec; 1H NMR (DMSO-d6) δ 3.47 (s, 3H), 3.64 (s, 3H), 3.94 (s, 3H), 6.64 (s, 1H), 7.71 (s, 1H), 7.75-7.90 (m, 2H), 8.08-8.15 (m, 1H), 8.29-8.43 (m, 1H), 8.57 (s, 1H), 13.27 (br s, 1H); EIMS m/z 411 (M+), 379 (base). 1-(2-Bromo-4-pyridyl)-6,7-dimethoxy-2-(methoxycarbonyl)naphthalene-3-carboxylic acid (12j): yield 98%; mp 223-225 °C dec; 1H NMR (CDCl3) δ 3.69 (s, 3H), 3.81 (s, 3H), 4.05 (s, 3H), 6.67 (s, 1H), 7.30 (s, 1H), 7.34 (dd, 1H, J ) 5.0, 1.4 Hz), 7.56-7.62 (m, 1H), 8.55 (d, 1H, J ) 5.0 Hz), 8.61 (s, 1H); EIMS m/z 445/447 (M+), 413/415 (base). 6,7-Dimethoxy-2-(methoxycarbonyl)-1-(2-thienyl)naphthalene-3-carboxylic acid (12k): yield 99%; mp 225-227 °C dec; 1H NMR (DMSO-d6) δ 3.54 (s, 3H), 3.69 (s, 3H), 3.93 (s, 3H), 6.99 (s, 1H), 7.11 (dd, 1H, J ) 3.5, 1.2 Hz), 7.22 (dd, 1H, J ) 5.1, 3.5 Hz), 7.67 (s, 1H), 7.78 (dd, 1H, J ) 5.1, 1.2 Hz), 8.54 (s, 1H), 13.04-13.45 (br s, 1H); EIMS m/z 372 (M+), 340 (base). 6,7-Dimethoxy-2-(methoxycarbonyl)-1-(3,4,5-trimethoxystyryl)naphthalene-3-carboxylic acid (12l): yield 93%; mp 239-240 °C dec; 1H NMR (DMSO-d6) δ 3.69 (s, 3H), 3.74 (s, 3H), 3.85 (s, 6H), 3.92 (s, 3H), 3.93 (s, 3H), 6.77 (d, 1H, J ) 16 Hz), 6.96 (s, 2H), 7.43 (s, 1H), 7.58 (d, 1H, J ) 16 Hz), 7.61 (s, 1H), 8.40 (s, 1H), 13.12 (br s, 1H); SIMS m/z 482 (M+, base), 451. 1-(3-Bromo-4,5-dimethoxyphenyl)-6-ethoxy-7-methoxy2-(methoxycarbonyl)naphthalene-3-carboxylic acid (12m): yield 86%; mp 223-224 °C dec; 1H NMR (CDCl3) δ 1.57 (t, 3H, J ) 6.9 Hz), 3.70 (s, 3H), 3.80 (s, 3H), 3.85 (s, 3H), 3.96 (s, 3H), 4.26 (q, 2H, J ) 7.0 Hz), 6.87 (s, 1H), 6.91 (d, 1H, J ) 1.9 Hz), 7.19 (d, 1H, J ) 1.9 Hz), 7.26 (s, 1H), 8.55 (s, 1H); EIMS m/z 518/520 (M+), 486/488 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-6,7,8-trimethoxy-2(methoxycarbonyl)naphthalene-3-carboxylic acid (12n): yield 93%; mp 231-232 °C dec; 1H NMR (CDCl3) δ 3.36 (s, 3H), 3.61 (s, 3H), 3.83 (s, 3H), 3.93 (s, 3H), 3.94 (s, 3H), 4.02 (s, 3H), 6.84 (d, 1H, J ) 1.9 Hz), 7.10 (d, 1H, J ) 1.9 Hz), 7.13 (s, 1H), 8.56 (s, 1H); EIMS m/z 534/536 (M+), 502/504 (base), 424. 1-(3-Bromo-4,5-dimethoxyphenyl)-2-(methoxycarbonyl)naphthalene-3-carboxylic acid (12o): yield 83%; mp 188-191 °C; 1H NMR (CDCl3) δ 3.72 (s, 3H), 3.85 (s, 3H), 3.97 (s, 3H), 6.90 (d, 1H, J ) 1.9 Hz), 7.17 (d, 1H, J ) 1.9 Hz), 7.54-7.73 (m, 3H), 7.98-8.10 (m, 1H), 8.75 (s, 1H), 10.0010.78 (br s, 1H); EIMS m/z 444/446 (M+), 412/414 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-6-methoxy-2-(methoxycarbonyl)naphthalene-3-carboxylic acid (12p): yield 93%; mp 206-208 °C; 1H NMR (CDCl3) δ 3.70 (s, 3H), 3.85 (s, 3H), 3.96 (s, 6H), 6.88 (d, 1H, J ) 1.9 Hz), 7.15 (d, 1H, J ) 1.9 Hz), 7.21-7.35 (m, 2H), 7.55 (d, 1H, J ) 9.1 Hz), 8.52 (s, 1H); EIMS m/z 474/476 (M+), 442/444 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-5-chloro-2-(methoxycarbonyl)naphthalene-3-carboxylic acid (12q): yield 93%; mp 202-204 °C; 1H NMR (DMSO-d6) δ 3.57 (s, 3H), 3.81 (s, 3H), 3.84 (s, 3H), 7.03 (d, 1H, J ) 1.9 Hz), 7.10 (d, 1H, J ) 1.9 Hz), 7.50-7.76 (m, 2H), 7.93 (dd, 1H, J ) 7.3, 1.1 Hz), 8.90 (s, 1H); EIMS m/z 478/480 (M+), 446/448 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-7-chloro-2-(methoxycarbonyl)naphthalene-3-carboxylic acid (12r): yield 71%; mp 215-217 °C dec; 1H NMR (CDCl3) δ 3.70 (s, 3H), 3.86 (s, 3H), 3.98 (s, 3H), 6.86 (d, 1H, J ) 1.9 Hz), 7.14 (d, 1H, J ) 1.9 Hz), 7.52-7.65 (m, 2H), 7.97 (d, 1H, J ) 7.9 Hz), 8.71 (s, 1H); EIMS m/z 478/480 (M+), 446/448 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-2-(methoxycarbonyl)7-methylnaphthalene-3-carboxylic acid (12s): yield 83%; mp 214-216 °C dec; 1H NMR (CDCl3) δ 2.48 (s, 3H), 3.70 (s, 3H), 3.85 (s, 3H), 3.98 (s, 3H), 6.88 (d, 1H, J ) 1.9 Hz), 7.15 (d, 1H, J ) 1.9 Hz), 7.36 (s, 1H), 7.46 (dd, 1H, J ) 8.4, 1.4 Hz), 7.93 (d, 1H, J ) 8.3 Hz), 8.70 (s, 1H); EIMS m/z 458/460 (M+), 426/428 (base). 3-Amino-6,7-dimethoxy-2-(methoxycarbonyl)-1-(3,4,5trimethoxyphenyl)naphthalene (13). To a mixture of 12a (15.0 g, 35 mmol) and triethylamine (21.2 g, 210 mmol) in THF



(300 mL) was added dropwise ethyl chloroformate (7.6 g, 70 mmol) in 50 mL of THF at -50 °C. After the mixture stirred at 0 °C for 30 min, 6.8 g of NaN3 in H2O (50 mL) was added to the mixture in one portion. After the mixture stirred at room temperature for 30 min, the mixture was diluted with CHCl3 and washed with brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure. The residue was dissolved in toluene (100 mL) and refluxed for 1 h. After cooling to room temperature, 70 mL of concentrated hydrochloric acid (70 mL) was added and the mixture was heated at 100 °C for 10 min. The reaction mixture was extracted with CHCl3 and washed with brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (n-hexaneAcOEt ) 1:1) gave 13 (8.9 g, 59%): mp 168-170 °C; 1H NMR (CDCl3) δ 3.47 (s, 3H), 3.73 (s, 3H), 3.83 (s, 6H), 3.94 (s, 6H), 4.21 (br s, 2H), 6.57 (s, 2H), 6.86 (s, 1H), 6.91 (s, 2H); EIMS m/z 427 (M+). 3-Amino-2-(hydroxymethyl)-6,7-dimethoxy-1-(3,4,5-trimethoxyphenyl)naphthalene (14). To a stirred suspension of lithium aluminum hydride (LiAlH4) (72 mg, 1.88 mmol) in THF (10 mL) was added 13 (400 mg, 0.94 mmol) in 10 mL of THF at 5 °C, and the mixture was stirred at the same temperature for 1 h. H2O (0.07 mL), 15% aqueous NaOH (0.07 mL), and H2O (0.21 mL) were added dropwise to the reaction mixture successively, and the resultant mixture was stirred at room temperature overnight. The precipitate was removed by filtration, and the filtrate was concentrated under reduced pressure. Crystallization of the residue from n-hexane-AcOEt (1:1) gave 14 (320 mg, 85%): mp 114-115 °C; 1H NMR (CDCl3) δ 3.50-4.30 (m, 3H), 3.66 (s, 3H), 3.78 (s, 6H), 3.93 (s, 6H), 4.57 (s, 2H), 6.50 (s, 2H), 6.65 (s, 1H), 6.88 (s, 1H), 6.92 (s, 1H); EIMS m/z 400 (M+), 381. 3-(Hydroxymethyl)-6,7-dimethoxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylic Acid Lactone (15). To mixture of 12a (2.0 g, 4.38 mmol) and triethylamine (443 mg, 4.38 mmol) in THF (20 mL) was added dropwise ethyl chloroformate (475 mg, 4.38 mmol) in 10 mL of THF at -5 to 0 °C. After stirring at 0 °C for 10 min, the precipitate was filtered off and washed with THF. The filtrate was added dropwise to a solution of NaBH4 (414 mg, 10.6 mmol) in 50% H2O-THF (v/v) (20 mL) at 0-5 °C. After stirring at room temperature for 1 h, the reaction mixture was poured into H2O and extracted with AcOEt. The organic layer was dried over MgSO4 and concentrated under reduced pressure. To a solution of the obtained residue in DMF (25 mL) was added NaH (62% dispersion in mineral oil, 204 mg, 5.26 mmol) at room temperature, and the mixture was stirred at room temperature for 3 h. The reaction mixture was quenched with the addition of H2O and extracted with AcOEt. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. Crystallization of the residue from Et2O gave 15 (1.52 g, 85%): mp 233-235 °C; 1H NMR (CDCl3) δ 3.80 (s, 3H), 3.86 (s, 3H), 3.98 (s, 3H), 4.06 (s, 3H), 5.41 (s, 2H), 6.62 (s, 2H), 7.15 (s, 1H), 7.20 (s, 1H), 7.73 (s, 1H); EIMS m/z 410 (M+, base), 395. 6,7-Dimethoxy-2-(methoxycarbonyl)-1-(3,4,5-trimethoxyphenyl)-3-naphthalenecarboxamide (16). To a mixture of 12a (500 mg, 1.1 mmol), 1-(3-dimethylaminopropyl)-3ethylcarbodiimide hydrochloride (EDCI‚HCl) (230 mg, 1.2 mmol), and 1-hydroxybenzotriazole hydrate (HOBt‚1H2O) (184 mg, 1.2 mmol) in DMF (5 mL) was added 28% aqueous NH3 (167 µL, 1.2 mmol), and the mixture was stirred at room temperature for 3 h. The mixture was poured into H2O and extracted with AcOEt. The organic layer was washed successively with saturated aqueous NaHCO3 and brine, dried over MgSO4, and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (CHCl3-MeOH ) 20:1) gave 16 (330 mg, 66%): mp 206-207 °C; 1H NMR (CDCl3) δ 3.63 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.95 (s, 3H), 4.02 (s, 3H), 5.70-6.42 (br s, 2H), 6.61 (s, 2H), 6.97 (s, 1H), 7.20 (s, 1H), 8.02 (s, 1H); SIMS m/z 456 (M+ + 1), 439, 424 (base). Anal. (C24H25NO8) Calcd: C, 60.88; H, 5.75; N, 2.96. Found: C, 61.05; H, 5.30; N, 2.87.

N-Methyl-6,7-dimethoxy-2-(methoxycarbonyl)-1-(3,4,5trimethoxyphenyl)-3-naphthalenecarboxamide (17) and 6,7-Dimethoxy-2-phenyl-9-(3,4,5-trimethoxyphenyl)benz[f]isoindole-1,3-dione (28). To a mixture of 12a (500 mg, 1.1 mmol), EDCI‚HCl (230 mg, 1.2 mmol), and HOBt‚1H2O (184 mg, 1.2 mmol) in DMF (5 mL) was added 40% aqueous MeNH2 (103 µL, 1.2 mmol), and the mixture was stirred at room temperature for 2 h. The mixture was poured into H2O and extracted with AcOEt. The organic layer was washed successively with saturated aqueous NaHCO3 and brine, dried over MgSO4, and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (from CHCl3acetone ) 10:1 to CHCl3-MeOH ) 20:1) gave 17 (23 mg, 4%) and 28 (320 mg, 67%), respectively. 17: mp 219-220 °C; 1H NMR (CDCl3) δ 3.03 (d, 3H, J ) 4.8 Hz), 3.62 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.02 (s, 3H), 6.14-6.32 (br d, 1H), 6.60 (s, 2H), 6.97 (s, 1H), 7.17 (s, 1H), 7.91 (s, 1H); EIMS m/z 469 (M+), 437 (base), 422. Anal. (C25H27NO7‚1.4H2O) Calcd: C, 60.69; H, 6.07; N, 2.83. Found: C, 60.67; H, 5.62; N, 2.82. 28: mp >250 °C; 1H NMR (CDCl3) δ 3.15 (s, 3H), 3.81 (s, 3H), 3.86 (s, 6H), 3.99 (s, 3H), 4.07 (s, 3H), 6.62 (s, 2H), 7.14 (s, 1H), 7.32 (s, 1H), 8.19 (s, 1H); EIMS m/z 437 (M+ base), 422. N,N-Dimethyl-6,7-dimethoxy-2-(methoxycarbonyl)-1(3,4,5-trimethoxyphenyl)-3-naphthalenecarboxamide (18). To a solution of 12a (500 mg, 1.1 mmol) in DMF (5 mL) was added 1,1′-carbonyldiimidazole (CDI) (213 mg, 1.31 mmol). After stirring at room temperature for 1 h, 50% aqueous Me2NH (118 mg, 1.31 mmol) was added and the mixture was stirred at room temperature overnight. The mixture was poured into H2O and extracted with AcOEt. The organic layer was washed successively with saturated aqueous NaHCO3 and brine, dried over MgSO4, and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (CHCl3-acetone ) 10:1) afforded 18 (396 mg, 75%): mp 190-192 °C; 1H NMR (CDCl3) δ 3.10 (s, 6H), 3.55 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.95 (s, 3H), 4.03 (s, 3H), 6.60 (s, 2H), 7.03 (s, 1H), 7.14 (s, 1H), 7.64 (s, 1H); EIMS m/z 483 (M+), 439 (base). General Procedure for the Preparation of 19-24. Compounds 19-24 were essentially prepared by the same procedure. The sequence is illustrated for 19, followed by analytical data for 20-24. 6,7-Dimethoxy-2-(methoxycarbonyl)-3-(1-pyrrolidinylcarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (19). To a mixture of 12a (500 mg, 1.1 mmol), EDCI‚HCl (230 mg, 1.2 mmol), and HOBt‚1H2O (184 mg, 1.2 mmol) in DMF (5 mL) was added pyrrolidine (100 µL,1.2 mmol), and the mixture was stirred at room temperature overnight. The mixture was poured into H2O and extracted with AcOEt. The organic layer was washed successively with saturated aqueous NaHCO3 and brine, dried over MgSO4, and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (CHCl3-MeOH ) 20:1) gave 19 (506 mg, 91%): mp 196198 °C; 1H NMR (CDCl3) δ 1.83-2.08 (m, 4H), 3.39-3.78 (m, 4H), 3.56 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.03 (s, 3H), 6.59 (s, 2H), 7.02 (s, 1H), 7.15 (s, 1H), 7.69 (s, 1H); EIMS m/z 509 (M+), 477, 439 (base). 6,7-Dimethoxy-2-(methoxycarbonyl)-3-(piperidinocarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (20): yield 90%; mp 170-172 °C; 1H NMR (CDCl3) δ 1.50-1.80 (m, 6H), 3.34-3.90 (m, 4H), 3.57 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.03 (s, 3H), 6.60 (s, 2H), 7.03 (s, 1H), 7.14 (s, 1H), 7.61 (s, 1H); EIMS m/z 523 (M+), 491, 439 (base). 6,7-Dimethoxy-2-(methoxycarbonyl)-3-(4-methyl-1-piperazinylcarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (21): yield 65%; mp 136-138 °C; 1H NMR (CDCl3) δ 2.31-2.60 (m, 4H), 2.35 (s, 3H), 3.45-3.61 (m, 2H), 3.57 (s, 3H), 3.69-3.90 (m, 2H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.03 (s, 3H), 6.59 (s, 2H), 7.02 (s, 1H), 7.15 (s, 1H), 7.62 (s, 1H); EIMS m/z 538 (M+), 455 (base), 439. 6,7-Dimethoxy-2-(methoxycarbonyl)-3-[4-(ethoxycarbonyl)piperidinocarbonyl]-1-(3,4,5-trimethoxyphenyl)-

1302


Ukita et al.

naphthalene (22): yield 96%; mp 137-139 °C; 1H NMR (CDCl3) δ 1.28 (t, 3H, J ) 7.13 Hz), 1.50-2.10 (m, 5H), 2.502.70 (m, 1H), 2.95-3.32 (m, 2H), 3.57 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.03 (s, 3H), 4.17 (q, 2H, J ) 7.13 Hz), 4.46-4.68 (m, 1H), 6.59 (s, 2H), 7.03 (s, 1H), 7.15 (s, 1H), 7.60 (s, 1H); EIMS m/z 595 (M+), 563, 439 (base). 6,7-Dimethoxy-2-(methoxycarbonyl)-3-(morpholinocarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (23): yield 88%; mp 196-198 °C; 1H NMR (CDCl3) δ 3.45-3.61 (m, 2H), 3.57 (s, 3H), 3.62-3.90 (m, 6H), 3.79 (s, 3H), 3.84 (s, 6H), 3.95 (s, 3H), 4.03 (s, 3H), 6.59 (s, 2H), 7.03 (s, 1H), 7.15 (s, 1H), 7.61 (s, 1H); EIMS m/z 525 (M+), 439 (base). 6,7-Dimethoxy-2-(methoxycarbonyl)-3-(4-oxopiperidinocarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (24): yield 92%; mp 188-190 °C; 1H NMR (CDCl3) δ 2.502.70 (m, 4H), 3.53 (s, 3H), 3.70-4.11 (m, 4H), 3.80 (s, 3H), 3.84 (s, 6H), 3.95 (s, 3H), 4.04 (s, 3H), 6.59 (s, 2H), 7.05 (s, 1H), 7.16 (s, 1H), 7.68 (s, 1H); EIMS m/z 537 (M+), 439 (base). Anal. (C29H33NO9) Calcd: C, 64.80; H, 5.81; N, 2.61. Found: C, 64.77; H, 5.98; N, 3.05. 6,7-Dimethoxy-2-(methoxycarbonyl)-3-(4-hydroxypiperidinocarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (25). To a stirred suspension of 24 (2.0 g, 3.72 mmol) in EtOH (20 mL) was added NaBH4 (70 mg, 1.86 mmol) at 0 °C, and the mixture was stirred at the same temperature for 30 min. The mixture was poured into H2O and extracted with AcOEt. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. Crystallization of the residue from AcOEt gave 25 (1.80 g, 90%): yield 90%; mp 224-227 °C; 1H NMR (CDCl3) δ 1.52-2.09 (m, 5H), 3.21-3.59 (m, 2H), 3.55 (s, 3H), 3.62-3.92 (m, 2H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.03 (s, 3H), 4.09-4.34 (m, 1H), 6.59 (s, 2H), 7.03 (s, 1H), 7.14 (s, 1H), 7.61 (s, 1H); EIMS m/z 539 (M+), 507, 439 (base). 6,7-Dimethoxy-2-(methoxycarbonyl)-3-(4-hydroxymethylpiperidinocarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (26). To a stirred mixture of 22 (2.0 g, 3.36 mmol) and NaBH4 (254 mg, 6.72 mmol) in THF (5 mL) was added dropwise MeOH (2.1 mL) under reflux over 1 h. The reaction mixture was allowed to cool to room temperature and concentrated under reduced pressure. The residue was poured into H2O and extracted with CH2Cl2. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (CHCl3-acetone ) 2:1) gave 26 (1.45 g, 78%): mp 218220 °C; 1H NMR (CDCl3) δ 1.23-1.49 (m, 2H), 1.61-1.99 (m, 3H), 2.70-3.28 (m, 2H), 3.48-3.68 (m, 3H), 3.56 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.03 (s, 3H), 4.62-4.89 (m, 1H), 6.59 (s, 2H), 7.02 (s, 1H), 7.14 (s, 1H), 7.61 (s, 1H); EIMS m/z 553 (M+), 521, 439 (base). General Procedure for the Preparation of 27a-n. Compounds 27a-n were essentially prepared by the same procedure. The sequence is illustrated for 27a, followed by analytical data for 27b-n. 3-[4-(2-Hydroxyethyl)-1-piperazinylcarbonyl]-6,7dimethoxy-2-(methoxycarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (27a). To a mixture of 12a (59.4 g, 0.13 mol), 1-(2-hydroxyethyl)piperazine (17.5 mL, 0.143 mol), and HOBt‚1H2O (21.9 g, 0.143 mol) in CH2Cl2 (300 mL) was added 1,3-dicyclohexylcarbodiimide (DCC) (29.5 g, 0.143 mol), and the mixture was stirred at room temperature overnight. The precipitate was filtered off and washed with CH2Cl2. The filtrate was washed successively with saturated aqueous NaHCO3 and brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (CHCl3-MeOH ) 20:1) gave 27a (32.0 g, 88%): mp 173-176 °C;1H NMR (CDCl3) δ 2.45-2.74 (m, 7H), 3.42-4.00 (m, 6H), 3.57 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.03 (s, 3H), 6.59 (s, 2H), 7.03 (s, 1H), 7.15 (s, 1H), 7.61 (s, 1H); SIMS m/z 569 (M+ + 1, base), 537, 469. 1-(3-Amino-4,5-dimethoxy)-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-6,7-dimethoxy-2-(methoxycarbonyl)1-(3,4,5-trimethoxyphenyl)naphthalene (27b): yield 38%;

mp 113-117 °C dec; 1H NMR (CDCl3) δ 1.54-2.30 (br s, 2H), 2.40-2.72 (m, 7H), 3.40-4.18 (m, 4H), 3.57 (s, 3H), 3.65 (t, 2H, J ) 5.4 Hz), 3.80 (s, 3H), 3.81 (s, 3H), 3.91 (s, 3H), 4.02 (s, 3H), 6.33 (d, 1H, J ) 1.8 Hz), 6.38, (d, 1H, J ) 1.8 Hz), 7.09 (s, 1H), 7.12 (s, 1H), 7.58 (s, 1H); SIMS m/z 554 (M+ + 1), 522, 424 (base). 1-(3-Chloro-4,5-dimethoxy)-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-6,7-dimethoxy-2-(methoxycarbonyl)1-(3,4,5-trimethoxyphenyl)naphthalene (27c): yield 87%; mp 155-158 °C; 1H NMR (CDCl3) δ 1.50-2.41 (m, 2H), 2.582.84 (m, 5H), 3.47-3.93 (m, 6H), 3.57 (s, 3H), 3.80 (s, 3H), 3.85 (s, 3H), 3.97 (s, 3H), 4.03 (s, 3H), 6.83 (d, 1H, J ) 1.8 Hz), 6.91 (s, 1H), 6.97 (d, 1H, J ) 1.8 Hz), 7.15 (s, 1H), 7.62 (s, 1H); SIMS m/z 573 (M+ + 1), 541, 443 (base). 1-(3-Bromo-4,5-dimethoxy)-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-6,7-dimethoxy-2-(methoxycarbonyl)1-(3,4,5-trimethoxyphenyl)naphthalene (27d): yield 78%; mp 167-168 °C; 1H NMR (CDCl3) δ 2.45-2.80 (m, 7H), 3.404.00 (m, 6H), 3.59 (s, 3H), 3.80 (s, 3H), 3.85 (s, 3H), 3.95 (s, 3H), 4.03 (s, 3H), 6.88 (d, 1H, J ) 1.9 Hz), 6.91 (s, 1H), 7.137.15 (m, 2H), 7.62 (s, 1H); EIMS m/z 616/618 (M+), 585/587, 487/489, 99 (base). 3-[4-(2-Hydroxyethyl)-1-piperazinylcarbonyl]-6,7dimethoxy-2-(methoxycarbonyl)-1-(2-methyl-4,5-dimethoxyphenyl)naphthalene (27e): yield 55%; mp 120-122 °C; 1H NMR (CDCl ) δ 1.95 (s, 3H), 2.45-2.71 (m, 7H), 3.41-4.01 3 (m, 6H), 3.54 (s, 3H), 3.73 (s, 3H), 3.80 (s, 3H), 3.95 (s, 3H), 4.03 (s, 3H), 6.67 (s, 1H), 6.69 (s, 1H), 6.82 (s, 1H), 7.15 (s, 1H), 7.63 (s, 1H); EIMS m/z 552 (M+), 534, 521, 439, 423 (base). 3-[4-(2-Hydroxyethyl)-1-piperazinylcarbonyl]-6,7dimethoxy-2-(methoxycarbonyl)-1-(3,4-methylenedioxyphenyl)naphthalene (27f): yield 94%; mp 186-188 °C; 1H NMR (CDCl ) δ 2.43-2.78 (m, 7H), 3.40-4.00 (m, 6H), 3.59 3 (s, 3H), 3.79 (s, 3H), 4.02 (s, 3H), 6.03 (d, 1H, J ) 1.3 Hz), 6.07 (d, 1H, J ) 1.3 Hz), 6.71-7.01 (m, 4H), 7.14 (s, 1H), 7.61 (s, 1H); EIMS m/z 522 (M+), 504, 491, 409, 393 (base). 1-(3,4-Dichlorophenyl)-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-6,7-dimethoxy-2-(methoxycarbonyl)naphthalene (27g): yield 69%; mp 179-180 °C; 1H NMR (CDCl3) δ 2.43-2.72 (m, 7H), 3.49-3.94 (m, 6H), 3.58 (s, 3H), 3.78 (s, 3H), 4.03 (s, 3H), 6.76 (s, 1H), 7.15 (s, 1H), 7.21 (dd, 1H, J ) 8.2, 2.0 Hz), 7.46 (d, 1H, J ) 1.9 Hz), 7.56 (d, 1H, J ) 8.2 Hz), 7.65 (s, 1H); EIMS m/z 546 (M+), 528, 515, 417 (base). 1-(3,5-Dichlorophenyl)-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-6,7-dimethoxy-2-(methoxycarbonyl)naphthalene (27h): yield 67%; mp 126-128 °C; 1H NMR (CDCl3) δ 2.43-2.72 (m, 7H), 3.39-4.00 (m, 6H), 3.59 (s, 3H), 3.80 (s, 3H), 4.03 (s, 3H), 6.75 (s, 1H), 7.15 (s, 1H), 7.26 (s, 2H), 7.46 (t, 1H, J ) 1.9 Hz), 7.65 (s, 1H); EIMS m/z 546 (M+), 528, 515, 417 (base). 3-[4-(2-Hydroxyethyl)-1-piperazinylcarbonyl]-6,7dimethoxy-2-(methoxycarbonyl)-1-(3-nitrophenyl)naphthalene (27i): yield 52%; mp 147-150 °C; 1H NMR (CDCl3) δ 2.26-2.90 (m, 7H), 3.47-4.15 (m, 6H), 3.52 (s, 3H), 3.72 (s, 3H), 4.04 (s, 3H), 6.65 (s, 1H), 7.19 (s, 1H), 7.62-7.80 (m, 3H), 8.23 (d, 1H, J ) 1.0 Hz), 8.28-8.41 (m, 1H); EIMS m/z 523 (M+), 505, 492, 394 (base). 1-(2-Bromo-4-pyridyl)-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-6,7-dimethoxy-2-(methoxycarbonyl)naphthalene (27j): yield 59%; mp 204-205 °C; 1H NMR (CDCl3) δ 2.46-2.74 (m, 7H), 3.40-3.99 (m, 6H), 3.59 (s, 3H), 3.78 (s, 3H), 4.04 (s, 3H), 6.66 (s, 1H), 7.16 (s, 1H), 7.21-7.35 (m, 1H), 7.51 (s, 1H), 7.68 (s, 1H), 9.51 (d, 1H, J ) 5.0 Hz); EIMS m/z 557/559 (M+), 539/541, 526/528, 428/430 (base). 3-[4-(2-Hydroxyethyl)-1-piperazinylcarbonyl]-6,7dimethoxy-2-(methoxycarbonyl)-1-(2-thienyl)naphthalene (27k): yield 83%; mp 190-192 °C; 1H NMR (CDCl3) δ 2.46-2.74 (m, 7H), 3.43-3.93 (m, 6H), 3.59 (s, 3H), 3.82 (s, 3H), 4.03 (s, 3H), 7.05-7.22 (m, 4H), 7.49 (dd, 1H, J ) 5.1, 1.2 Hz), 7.64 (s, 1H); SIMS m/z 485 (M+ + 1), 453, 355 (base). 3-[4-(2-Hydroxyethyl)-1-piperazinylcarbonyl]-6,7dimethoxy-2-(methoxycarbonyl)-1-(3,4,5-trimethoxystyryl)naphthalene (27l): yield 73%; mp 123-125 °C; 1H NMR (CDCl3) δ 2.42-2.74 (m, 7H), 3.41-3.60 (m, 2H), 3.65 (t, 1H,



J ) 5.1 Hz), 3.78-3.90 (m, 2H), 3.81 (s, 3H), 3.89 (s, 3H), 3.92 (s, 6H), 3.97 (s, 3H), 4.03 (s, 3H), 6.68 (d, 1H, J ) 16 Hz), 6.76 (s, 2H), 7.13 (s, 1H), 7.42 (s, 1H), 7.51 (d, 1H, J ) 16 Hz), 7.55 (s, 1H); EIMS m/z 594 (M+), 99 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-6-ethoxy-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-7-methoxy-2-(methoxycarbonyl)naphthalene (27m): yield 85%; mp 110-112 °C; 1H NMR (CDCl3) δ 1.56 (t, 3H, J ) 7.0 Hz), 2.42-2.73 (m, 7H), 3.41-4.02 (m, 6H), 3.59 (s, 3H), 3.79 (s, 3H), 3.85 (s, 3H), 3.95 (s, 3H), 4.25 (q, 2H, J ) 7.0 Hz), 6.88 (d, 1H, J ) 1.8 Hz), 6.91 (s, 1H), 7.13 (s, 1H), 7.14 (s, 1H), 7.60 (s, 1H); EIMS m/z 630/632 (M+), 599/601, 501/503, 99, 56 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-3-[4-(2-hydroxyethyl)1-piperazinylcarbonyl]-6,7,8-trimethoxy-2-(methoxycarbonyl)naphthalene (27n): yield 81%; mp 148-150 °C; 1H NMR (CDCl3) δ 2.41-2.76 (m, 7H), 3.30-4.10 (m, 4H), 3.35 (s, 3H), 3.50 (s, 3H), 3.64 (t, 2H, J ) 5.2 Hz), 3.83 (s, 3H), 3.89 (s, 3H), 3.91 (s, 3H), 4.00 (s, 3H), 6.84 (d, 1H, J ) 1.8 Hz), 6.98 (s, 1H), 7.07 (d, 1H, J ) 1.8 Hz), 7.61 (s, 1H); EIMS m/z 646/648 (M+), 615/618, 517/519 (base), 439. General Procedure for the Preparation of 27o-s. Compounds 27o-s were essentially prepared by the same procedure. The sequence is illustrated for 27o, follwed by analytical data for 27p-s. 1-(3-Bromo-4,5-dimethoxyphenyl)-3-[4-(2-hydroxyethyl)1-piperazinylcarbonyl]-2-(methoxycarbonyl)naphthalene Hydrochloride (27o). To a mixture of 12o (2.0 g, 4.49 mmol), 1-(2-hydroxyethyl)piperazine (660 µL, 4.94 mol), and HOBt‚1H2O (668 mg, 4.94 mmol) in CH2Cl2 (40 mL) was added DCC (1.02 g, 4.94 mmol), and the mixture was stirred at room temperature overnight. The precipitate was filtered off and washed with CH2Cl2. The filtrate was washed successively with saturated aqueous NaHCO3 and brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (CHCl3-MeOH ) 20:1) gave 1-(3-bromo-4,5-dimethoxyphenyl)3-[4-(2-hydroxyethyl)piperazinocarbonyl]-2-(methoxycarbonyl)naphthalene. After addition of 2 N hydrochloric acid (2.05 mL, 4.1 mmol) to a solution of the obtained free base (1.9 g, 3.41 mmol) in CHCl3 (40 mL), the mixture was concentrated under reduced pressure. Crystallization of the residual salt from AcOEt gave 27o (1.76 g, 66%): mp 173-175 °C dec; 1H NMR (DMSO-d6) δ 2.90-3.96 (m, 11H), 3.54 (s, 3H), 3.82 (s, 3H), 3.85 (s, 3H), 4.40-4.59 (m, 1H), 5.39 (br s, 1H), 7.04 (s, 1H), 7.07 (s, 1H), 7.59-7.81 (m, 3H), 8.07-8.18 (m, 1H), 8.33 (s, 1H), 11.04 (br s, 1H); SIMS m/z 557/559 (M+ + 1-HCl), 525/ 527, 427/429 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-3-[4-(2-hydroxyethyl)1-piperazinylcarbonyl]-7-methoxy-2-(methoxycarbonyl)naphthalene hydrochloride (27p): yield 57%; mp 159-162 °C; 1H NMR (DMSO-d6) δ 2.91-4.08 (m, 11H), 3.52 (s, 3H), 3.81 (s, 3H), 3.84 (s, 3H), 3.92 (s, 3H), 4.41-4.69 (m, 1H), 5.41 (br s, 1H), 7.00 (s, 1H), 7.04 (s, 1H), 7.29 (dd, 1H, J ) 9.2, 2.6 Hz), 7.44-7.61 (m, 2H), 8.00 (s, 1H), 10.97 (br s, 1H); EIMS m/z 586/588 (M+ - HCl), 568/570, 555/557, 457/459 (base). 1-(3-Bromo-4,5-dimethoxyphenyl)-5-chloro-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-2-(methoxycarbonyl)naphthalene hydrochloride (27q): yield 67%; mp 230235 °C dec; 1H NMR (DMSO-d6) δ 2.96-4.06 (m, 11H), 3.56 (s, 3H), 3.82 (s, 3H), 3.85 (s, 3H), 4.35-4.67 (m, 1H), 5.38 (br s, 1H), 7.06 (s, 1H), 7.11 (d, 1H, J ) 1.5 Hz), 7.58-7.71 (m, 2H), 7.88-8.01 (m, 1H), 8.31 (s, 1H), 11.15 (br s, 1H); SIMS m/z 591/593 (M+ + 1 - HCl, base), 559/561, 491/493. 1-(3-Bromo-4,5-dimethoxyphenyl)-7-chloro-3-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-2-(methoxycarbonyl)naphthalene hydrochloride (27r): yield 66%; mp 156158 °C dec; 1H NMR (DMSO-d6) δ 2.89-4.01 (m, 11H), 3.53 (s, 3H), 3.82 (s, 3H), 3.85 (s, 3H), 4.40-4.70 (m, 1H), 5.40 (br s, 1H), 7.06 (s, 1H), 7.11 (s, 1H), 7.56 (d, 1H, J ) 1.9 Hz), 7.77 (dd, 1H, J ) 8.7, 2.1 Hz), 8.10-8.26 (m, 2H), 10.77 (br s, 1H); SIMS m/z 591/593 (M+ + 1 - HCl, base), 559/561, 461/463. 1-(3-Bromo-4,5-dimethoxyphenyl)-3-[4-(2-hydroxyethyl)1-piperazinylcarbonyl]-2-(methoxycarbonyl)-7-methylnaphthalene hydrochloride (27s): yield 77%; mp 230-231

°C dec; 1H NMR (DMSO-d6) δ 2.43 (s, 3H), 2.90-4.06 (m, 11H), 3.52 (s, 3H), 3.82 (s, 3H), 3.85 (s, 3H), 4.40-4.68 (m, 1H), 5.40 (br s, 1H), 7.02 (s, 1H), 7.06 (d, 1H, J ) 1.6 Hz), 7.40 (s, 1H), 7.56 (d, 1H, J ) 8.4 Hz), 8.01 (d, 1H, J ) 8.4 Hz), 8.10 (s, 1H), 11.24 (br s, 1H); SIMS m/z 571/573 (M+ + 1 - HCl), 539/541, 441/443 (base). 3-Methyl-6,7-dimethoxy-2-(methoxycarbonyl)-1-(3,4,5trimethoxyphenyl)naphthalene (29). To a solution of acetal 1 [R1 ) 4,5-(OMe)2] (169 g, 0.58 mol) in THF (400 mL) was added dropwise n-BuLi (400 mL, 0.64 mol) at -78 °C under a nitrogen atmosphere, and the mixture was stirred at the same temperature for 30 min. A solution of 3,4,5-trimethoxybenzaldehyde (114 g, 0.58 mol) in THF (300 mL) was added dropwise at -70 °C over 30 min. After stirring at the same temperature for 1 h, the mixture was poured into H2O and extracted with AcOEt. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. A mixture of the obtained residue, methyl crotonate (67.7 mL, 0.64 mol), and acetic acid (180 mL) in toluene (180 mL) was heated under reflux for 1 h. After the addition of TFA (30 mL), the mixture was further refluxed for 2 h. The reaction mixture was poured into saturated aqueous NaHCO3 and extracted with CHCl3. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (n-hexane-CHCl3-AcOEt ) 10:5:1) gave 29 (10.7 g, 4.3%): mp 175-183 °C dec;1H NMR (CDCl3) δ 2.47 (s, 3H), 3.60 (s, 3H), 3.78 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.01 (s, 3H), 6.63 (s, 2H), 6.99 (s, 1H), 7.09 (s, 1H), 7.54 (s, 1H); EIMS m/z 426 (M+, base), 411. 3-(Bromomethyl)-6,7-dimethoxy-2-(methoxycarbonyl)1-(3,4,5-trimethoxyphenyl)naphthalene (30). A mixture of 29 (8.4 g, 19.7 mmol), N-bromosuccinimide (NBS) (3.86 g, 21.7 mmol), and benzoyl peroxide (200 mg) in CCl4 (300 mL) was heated under reflux overnight. The mixture was poured into H2O and extracted with AcOEt. The organic layer was washed successively with saturated aqueous NaHCO3 and brine, dried over MgSO4, and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (n-hexaneAcOEt ) 5:3) gave 30 (1.45 g, 14.6%): mp 180-181 °C; 1H NMR (CDCl3) δ 3.59 (s, 3H), 3.79 (s, 3H), 3.85 (s, 6H), 3.95 (s, 3H), 4.03 (s, 3H), 4.78 (s, 2H), 6.61 (s, 2H), 7.02 (s, 1H), 7.14 (s, 1H), 7.76 (s, 1H); EIMS m/z 504/506 (M+), 425 (base), 410, 94. 3-[4-(2-Hydroxyethyl)piperazinomethyl]-6,7-dimethoxy2-(methoxycarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene Dihydrochloride (31). To a stirred suspension of 30 (0.82 g, 1.62 mmol) in THF (10 mL) was added 1-(2hydroxyethyl)piperazine (0.40 mL, 3.24 mmol) at room temperature, and the mixture was stirred at room temperature for 4.5 h. The reaction mixture was concentrated under reduced pressure. The residue was diluted with CH2Cl2 and washed successively with saturated aqueous NaHCO3 and brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure. Purification of the residue by silica gel chromatography (CHCl3-MeOH ) 10:1) gave 3-[4(2-hydroxyethyl)piperazinomethyl]-6,7-dimethoxy-2-(methoxycarbonyl)-1-(3,4,5-trimethoxyphenyl)naphthalene (0.85 g, 95%): 1H NMR (CDCl3) δ 2.32-2.61 (m, 10H), 3.42-3.80 (m, 5H), 3.52 (s, 3H), 3.80 (s, 3H), 3.85 (s, 6H), 3.94 (s, 3H), 4.02 (s, 3H), 6.62 (s, 2H), 7.05 (s, 1H), 7.13 (s, 1H), 7.59 (s, 1H); EIMS m/z 554 (M+), 536, 523, 425 (base). After addition of 4 N HCl-dioxane (0.94 mL, 3.76 mmol) to a solution of the above free base (0.85 g, 1.5 mmol) in 10 mL of dioxane, the mixture was concentrated under reduced pressure. The residue was triturated with ether and the product 31 (0.86 g) was collected in 82% yield: mp 123-130 °C dec; 1H NMR (D2O) δ 2.44-4.02 (s, 13H), 3.21-3.37 (m, 2H), 3.62 (s, 3H), 3.68 (s, 3H), 3.73 (s, 6H), 3.80 (s, 2H), 3.94 (s, 3H), 3.98 (s, 3H), 6.47 (s, 2H), 6.76 (s, 1H), 7.04 (s, 1H), 7.40 (s, 1H); EIMS m/z 554 (M+ - 2HCl), 536, 523, 425 (base). 3-[4-(2-tert-Butyldimethylsilyloxyethyl)piperazinomethyl]-6,7-dimethoxy-2-(methoxycarbonyl)-1-(3,4,5trimethoxyphenyl)naphthalene (32). To a stirred suspen-

1304


sion of 27a (11.4 g, 20 mmol) in THF (40 mL) were added imidazole (2.04 g, 30 mmol) and tert-butyldimethylsilyl chloride (4.52 g, 30 mmol), and the mixture was stirred at room temperature overnight. The mixture was poured into H2O and extracted with AcOEt. The organic layer was washed successively with saturated NaHCO3 and brine, dried over MgSO4, and concentrated under reduced pressure. The residue was triturated with n-hexane, and the product 32 (13.1 g) was obtained in 96% yield: mp 95-98 °C; 1H NMR (CDCl3) δ 0.06 (s, 6H), 0.89 (s, 9H), 2.43-2.72 (m, 6H), 3.40-3.93 (m, 6H), 3.57 (s, 3H), 3.79 (s, 3H), 3.84 (s, 6H), 3.94 (s, 3H), 4.03 (s, 3H), 6.59 (s, 2H), 7.02 (s, 1H), 7.15 (s, 1H), 7.61 (s, 1H); EIMS m/z 682 (M+), 537, 439 (base). 3-[4-(2-Hydroxyethyl)piperazinomethyl]-2-(hydroxymethyl)-6,7-dimethoxy-1-(3,4,5-trimethoxyphenyl)naphthalene (33) and 3-[4-(2-Hydroxyethyl)piperazinocarbonyl]2-(hydroxymethyl)-6,7-dimethoxy-1-(3,4,5-trimethoxyphenyl)naphthalene (34). To a stirred suspension of LiAlH4 (2.67 g, 70.3 mmol) in THF (50 mL) was added dropwise 32 (12.0 g, 17.6 mmol) in 20 mL of THF at room temperature, and the mixture was stirred for 3 h. H2O (8.5 mL) and 2 N aqueous NaOH (5.7 mL) were added dropwise successively, and the resultant mixture was stirred at room temperature for 30 min. The precipitate was removed through a Celite pad, and the filtrate was concentrated under reduced pressure. Purification of the residue by silica gel chromatography (from CHCl3-MeOH ) 20:1 to CHCl3-MeOH ) 1:2) gave 33 (3.5 g, 38%) and 34 (1.5 g, 16%), respectively. 33: 1H NMR (CDCl3) δ 1.51-1.92 (br s, 1H), 2.31-2.90 (m, 10H), 3.50-3.90 (m, 5H), 3.75 (s, 3H), 3.85 (s, 6H), 3.96 (s, 3H), 4.01 (s, 3H), 4.50 (s, 2H), 6.61 (s, 2H), 6.85 (s, 1H), 7.13 (s, 1H), 7.60 (s, 1H); EIMS m/z 526 (M+), 396, 131 (base). 34: mp 188-191 °C; 1H NMR (CD3OD) δ 2.64 (t, 2H, J ) 5.8 Hz), 2.68-3.00 (m, 8H), 3.64-3.78 (m, 2H), 3.70 (s, 3H), 3.83 (s, 3H), 3.84 (s, 6H), 3.95 (s, 3H), 3.97 (s, 2H), 6.77 (s, 2H), 6.95 (s, 1H), 7.25 (s, 1H), 7.82 (s, 1H); SIMS m/z 541 (M+ + 1, base), 411. Biological Methods. Isolation of Phosphodiesterase Isozymes. The method of Reeves et al.11 was modified to isolate PDE isozymes: 1.0 g of lung, heart, or adrenal gland of 56-week-old beagle dog was homogenized in 10 mL ice-cold homogenization buffer (20 mM Tris/HCl, pH 7.8, 2 mM magnesium acetate, 0.3 mM CaCl2, 1 mM dithiothreitol, 40 µM leupeptin, 1.3 mM benzamidine, 0.2 mM phenylmethanesulfonyl fluoride, and 1 mM NaN3) in a Polytron homogenizer for 1 min at medium speed. The homogenate was centrifuged at 6000g for 20 min, and the supernatant was recentrifuged at 100000g for 60 min. The cytosolic fraction isolated above was applied to a DEAE-Sephadex column (Pharmacia) equilibrated in elution buffer (20 mM Tris/HCl, pH 7.8, 1 mM dithiothreitol, 1 mM CaCl2, 2 µM leupeptin, and 5 mM benzamidine). The column was washed with 10 mL of elution buffer, and the PDEs were then eluted from the column by running a linear NaCl gradient (0-400 mM, 50 mL; 400-2000 mM, 10 mL) in elution buffer. Fractions (1 mL each) were collected on ice and assayed for cGMP and cAMP hydrolytic PDE activity. Assay of Phosphodiesterase Activity. PDE activity was determined by a modification of the method of Thompson et al.12 The assay buffer contained 50 mM Tris-HCl, pH 8.0, 5 mM MgCl2, 4 mM 2-mercaptoethanol, 1 µM unlabeled cGMP or cAMP, and 22 nM [3H]cGMP or [3H]cAMP. The reaction was started by mixing 0.1-10 µM enzyme solution into 500 µL of assay buffer, and tubes were incubated at 37 °C for 30 min. After boiling for 1.5 min, the mixture was added to 100 µL of 1 mg/mL Crotalus atrox snake venom and incubated at 37 °C for 30 min. The reaction was quenched by the addition of 500 µL of methanol, and the resultant solution was applied to a Dowex (1 × 8-400) column. Aqueous scintillation cocktails were added to each elute, and the radioactivity was measured. Relaxing Effect on Isolated Coronary Arteries Precontracted with Phenylephrine. Relaxing effect was determined by a modification of the method of Ignarro et al.13 Porcine coronary arteries were removed, cleaned of adjacent

Ukita et al. tissues, and cut into rings with special care not to damage the endothelium. The rings were longitudinally opened and mounted in organ baths containing 10 mL of Krebs-Henseleit solution (37 °C, pH 7.4, bubbled with 95% O2-5% CO2). The coronary arterial strips were allowed to equilibrate under a resting tension of 1 g. The presence of intact endothelial cells was confirmed by bradykinin (final concentration, 7 × 10-9 M)induced relaxation of strips precontracted with KCl (final concentration, 50 mM). The strips were contracted with phenylephrine (final concentration, 3 × 10-6 M), and after the attainment of a plateau contraction, cumulative concentration-relaxation curves for a tested compound were constructed. Relaxation was calculated as a percentage of the contractile response to papaverine.

Acknowledgment. We express our great gratitude to Drs. K. Matsumoto, K. Kawashima, and T. Iwasaki of Tanabe Seiyaku Co., Ltd. for their encouragement and interest. References (1) (a) Beavo, J. A.; Conti, M.; Heaslip, R. J. Multiple Cyclic Nucleotide Phophodiesterase. Mol. Pharmacol. 1994, 46, 399405. (b) Beavo, J. A. Cyclic Nucleotide Phosphodiesterases: Functional Implications of Multiple Isoforms. Physiol. Rev. 1995, 75, 725-748. (2) (a) Czarniecki, M.; Ahn, H.-S.; Sybertz, E. J. Inhibitors of Types I and V Phophodiesterase: Elevation of cGMP as a Therapeutic Strategy. Annu. Rep. Med. Chem. 1996, 31, 61-70. (b) Eardley, I. The Role of Phosphodiesterase Inhibitors in Impotence. Exp. Opin. Invest. Drugs 1997, 6, 1803-1810. (3) (a) Dumaitre, B.; Dodic, N. Synthesis and Cyclic GMP Phosphodiesterase Inhibitory Activity of 6-Phenylpyrazolo[3,4-d]pyrimidones. J. Med. Chem. 1996, 39, 1635-1644. (b) Terrett, N. K.; Bell, A. S.; Brown, D.; Ellis, P. SILDENAFIL (VIAGRATM), A Potent and Selective Inhibitor of Type 5 cGMP Phosphodiesterase with Utility for the Treatment of Male Erectile Dysfunction. Bioorg. Med. Chem. Lett. 1996, 15, 1819-1824. (4) (a) Takase, Y.; Saeki, T.; Watanabe, N.; Adachi, H.; Souda, S.; Saito, I. Cyclic GMP Phophodiesterase Inhibitors. 2. Replacement of 6-Substitution of Quinazoline Derivatives for Potent and Selective Inhibitory Activity. J. Med. Chem. 1994, 37, 21042111. (b) Takase, Y.; Saeki, T.; Fujimoto, M.; Saito, I. Cyclic GMP Phophodiesterase Inhibitors. 1. The Discovery of a Novel Potent Inhibitor, 4-((3, 4-(Methylenedioxy)benzyl)amino)-6,7,8-trimethoxyquinazoline. J. Med. Chem. 1993, 36, 3765-3770. (c) Lee, S. J.; Konishi, Y.; Yu, D. T.; Miskowski, T. A.; Riviello, C. M.; Macina, O. T.; Frierson, M. R.; Kondo, K.; Sugitan, M.; Sircar, J. C.; Blazejewski, K. M. Discovery of Potent Cyclic GMP Phosphodiesterase Inhibitors. 2-Pyridyl- and 2-Imidazolylquinazolines Possessing Cyclic GMP Phophodiesterase and Thromboxane Synthesis Inhibitory Activities. J. Med. Chem. 1995, 38, 3547-3557. (5) Watanabe, N.; Kabasawa, Y.; Takase, Y.; Matsukura, M.; Miyazaki, K.; Ishihara, H.; Kodama, K.; Adachi, H. 4-Benzyl1-chloro-6-substituted Phthalazines: Synthesis and Inhibitory Activity toward Phosphodiesterase 5. J. Med. Chem. 1998, 41, 3367-3572. (6) Iwasaki, T.; Kondo, K.; Kuroda, T.; Moritani, Y.; Yamagata, S.; Sugiura, M.; Kikkawa, H.; Kaminuma, O.; Ikezawa, K. Novel Selective PDE IV Inhibitors as Antiasthmatic Agents. Synthesis and Biological Activities of a Series of 1-Aryl-2,3-bis(hydroxymethyl)naphthalene Lignans. J. Med. Chem. 1996, 39, 26962704. (7) Rodrigo, R. Progress in the Chemistry of Isobenzofurans; Application to the Synthesis of Natural Products and Polyaromatic Hydrocarbons. Tetrahedron 1988, 11, 2093-2135. (8) Plaumann, H. P.; Smith, J. G.; Rodigo, R. Potential Isobenzofurans: their Use in the Synthesis of Naturally Occurring 1-Arylnaphthalide Lignans. J. Chem. Soc. Chem. Commun. 1980, 354. (9) Weeratunga, G.; Rajapaksa, D.; Rodrigo, R. The Synthesis and Relative Configuration of (()-Lirionol. J. Org. Chem. 1985, 50, 5902-5905. (10) Sugahara, M.; Moritani, Y.; Terakawa, Y.; Ogiku, T.; Ukita, T.; Iwasaki, T. A Synthesis of 1-Pyridylnaphthalene lignan analogues. Tetrahedron Lett. 1998, 39, 1377-1380. (11) Reeves, M. L.; Leigh, B. K.; England, P. J. The Identification of a New Cyclic Nucleotide Phosphodiesterase Activity in the

1-Arylnaphthalene Lignan Human and Gunia-Pig Cardiac Ventricle. Biochem. J. 1987, 241, 535-541. (12) Thompson, W. J.; Terasaki, W.; Epstein, P. M.; Strada, S. J. Assay of Cyclic Nucleotide Phosphodiesterase and Resolution of Multiple Molecular Forms of the Enzyme. Adv. Cycl. Nucleotide Res. 1979, 10, 67-72.

Journal of Medicinal Chemistry, 1999, Vol. 42, No. 7 1305 (13) Ignarro, L. J.; Byrns, R. E.; Wood, K. S. Endothelium-dependent Modulation of cGMP Levels and Intrinsic Smooth Muscle Tone in Isolated Bovine Intrapulmonary Artery and Vein. Circ. Res. 1987, 60, 82-92.

JM9807048

1-Arylnaphthalene Lignan: A Novel Scaffold for Type 5

Recommend Documents